This invention relates to a scrubber for removing extraneous gaseous matter from water and steam.
For example, in the beverage industry, it is desirable to remove extraneous gaseous matter (air and oxygen) from the water to thereby provide "deaerated" water. This is done to achieve stability of the beverage during preparation and during the filling process, as well as during storage prior to consumption.
Moreover, following the filling process, extraneous gaseous matter can promote premature deterioration and instability of the beverage within the can, bottle or aseptic package. Hence, scrubbing of the water utilized in beverage preparation can greatly increase the shelf life of the packaged product as well.
In the prior art, attempts were made to promote stability of the product by holding the pressure of the product at a relatively low level during preparation and filling. Primarily, cooling apparatus was utilized to maintain such pressure control and promote beverage stability. However, with the advent of modern containers and high-speed filling apparatus, higher pressures may safely be utilized to increase filling line efficiency. Accordingly, mere cooling of the water may be unnecessary or even undesirable in such installations.
In modern beverage operations, a proportioning unit is utilized to mix water with one or more "syrups" some containing natural fruit juice to produce the finished beverage. In the case of diet-type beverages, the syrup contains no sugar, and hence is very low in solid content, consisting primarily of water. Accordingly, water devoid of extraneous gaseous matter may advantageously be used in syrup preparation for these diet beverages as well.
While the prior art deaerating apparatus has been widely accepted in the beverage industry, there is room for further improvement. In particular, it is desirable to coordinate the flow of water through the deaerating apparatus with the deaerated water requirements of the downstream utilization apparatus, such as beverage mixing or proportioning and beverage filling apparatus. The demand for deaerated water may vary considerably during process operation. During startup and shutdown of a beverage preparation and filling line, a varying demand for deaerated water is experienced at the scrubbing apparatus.
Similarly, scrubbing of the water introduced to boiler apparatus is known to reduce corrosion and thereby extend equipment life, to reduce pipeline and equipment replacement costs and to lower overall maintenance. In this regard, it has been determined that dissolved oxygen and carbon dioxide in the boiler water can be up to 40% more corrosive than equal quantities of either gas alone, especially at the higher temperatures experienced in a boiler. Hence, scrubbing of the boiler water, and particularly of makeup water, to remove dissolved oxygen and carbon dioxide is beneficial. In this instance, steam may be used as the scrubbing gas.
The prior art has attempted to control the flow of water through the deaerating apparatus by sensing the level of deaerated water accumulated at a bottom portion or reservoir thereof and available for use by downstream apparatus. However, the deaerating apparatus usually comprises a relatively tall column, wherein the water to be deaerated is introduced at the top of the column and is passed down through deaerating apparatus, generally against a counterflow of stripping gas such as nitrogen or carbon dioxide (or steam in a boiler application). Hence, at any given point in the process, a relatively large volume of water is in the deaerating column. Accordingly, controlling the flow of water to the top of the column by sensing the level of deaerated water at the bottom results in a considerable amount of excess deaerated water being produced (i.e., that water which is already within the column) after the signal to shut down is received. The same will be seen to be true of any control signal derived from equipment downstream of the deaerating apparatus for controlling the inflow of water to the top or inlet thereof.
The prior art has also proposed flow control apparatus located upstream of the deaerator column or apparatus for metering and controlling the flow of water thereto. One such flow control device is shown, for example, in U.S. Pat. No. 4,350,503. However, this device also achieves control based primarily upon the level of water at the bottom of the deoxygenating or deaerating column, and moreover comprises a relatively complex and expensive additional piece of equipment.